TO YELLOWSTONE NATIONAL PARK. 117 
The difficulty in settling the matter arose from the fact that the loose shale seldom showed its true 
position. 
We find this formation in the immediate vicinity of Camp Baker, both to the east, where it 
forms high hills 250 feet above the plain, also to the south and west, where it is intersected by some 
dikes of porphyry, and quite extensively below in the valley of Deep Creek, as well as along the 
valley of White-tailed Deer Creek. Its general distribution seems to conform to a certain extent 
to that of the Miocene Tertiary that is filling the valleys between the older rocks. 
The older rocks alluded to form the ranges of hills conspicuous about Camp Baker. Immedi- 
ately north of the post lies a range of hills, having an east and west trend, through which Deep 
River takes its course by means of a cation, which gives an excellent section of the rocks of which 
the hills are composed. The rocks all dip south, and this dip continues the same for a mile or two 
to the north. South of the range alluded to, and close to the post, are several minor hills, and, at a 
distance, a series of others all singularly alike in appearance. The section of rocks alluded to is 
as follows: Ss 
QOALtZILC eink! eka oe evan deen eee Sand ves lee eas Bees we ee te see ee 20 feet. 
A series of colored shales, chiefly red, but also green and blue, with a bed 
of ‘trachyte interstratified «. 2... veaies ec cesses ere ees ceie eee e wwe 150 feet. 
Two ridges of limestone, in all........... ee 80 feet. 
These limestones show abrupt bluffs to the north, and dip southerly. In the northernmost of 
the ridges were found— 
1. Crepicephalus (Loganellus) montanensis, Whitf. (n. sp.) ; 
2. Obolella, sp.? ; 
identifying the formation as Potsdam, according to Mr. Whitfield. Following this is a quartzite, 
which forms the south side of the hill alluded to. The section is continued through the cafion : 
quartzite 40 feet, firm and solid, with areddish tinge of color, breaking into massive blocks; under- 
neath is a series of bright green slates, followed by a variety of clay-slates, mostly dark-colored, 
with occasional beds of hard solid quartzite and some thin layers of limestone. After half a mile, 
the ridge is passed, and the stream comes out into the open country. The rocks, for a mile or two, 
however, are mostly the same in dip, and are conformable. They are chiefly dark blue shales. 
The appearance of the quartzite hills in this neighborhood is peculiar, as they all have a grad- 
ual slope to the south, but are nearly vertical toward the north, on which side there is at their foot 
a talus of large cubical blocks of quartzite. 
We were unfortunately not able to visit the Big Belt Mountains. 
CAMP BAKER TO FORT ELLIS. 
From Camp Baker, the party marched to Fort Ellis; the road for a short distance being the 
same as that before traveled. The road passes to the right of the Elk Range. Twenty miles from 
Camp Baker, we reached the extremity of this range. At this point, we passed immediately from 
the grassy meadow onto the older rocks. Here we found first a red shale similar to that at Camp 
Baker, and also to that observed higher up, four miles the other side of the Springs. This was fol- 
lowed by a heavy massive quartzite, a little reddish and very firm; and overlying this was a 
considerable thickness of limestone. This last is well exposed just above Moss Agate Springs, and 
in some of the layers we found an abundance of fragments of Trilobites. The limestone is much of 
it very cherty, and in many places it formed the same abrupt and peculiar shapes noticed elsewhere, 
Just above Moss Agate, there is a little superficial synclinal fold in the limestone, the axis of which 
has an approximately northeasterly direction. Moss Agate Springs takes its name from the frag- 
ments of flint, chalcedony, and agate, which are common on the adjoining hills, and many of which, 
from the presence of the arborescent forms of psilomelane, are popularly called ‘‘moss agates”. 
These fragments of silica are evidently from the limestene, and are quite characteristic of it. 
Similar fragments of chalcedony, though without the moss effect, were found abundantly in some 
of the little hills just by Camp Baker. The limestone is evidently the same as that, as is moreover 
proved by its association with the quartzite and by the few fossils found in it; these were all of one 
apecies, a new Trilobite,—Arionellus tripunctatus, Whitf. (n. sp.). 
